In the prior art, solutions are known for protected transmission of data objects over the internet. One form of protected data transmission is encrypted and/or signed emails. This form of data transmission is commonly used and standardised. However, the preparations for use of this technology are usually very complex, since before actual transmission of the data objects, one or more keys or certificates for encrypting the data must be exchanged between the sender and the addressee. So, in the case of an asymmetric encryption method, first the addressee must give the sender his public key for encrypting the data objects, so that the sender can then encrypt the data objects with the addressee's public key and transmit them in protected form to the addressee. The addressee can then decrypt the encrypted data objects with his private key. This is particularly complex if it does not involve closed user groups (e.g. within an organisation) in which central administration ensures smooth function. Also, in this form of protected data transmission, all data objects to be sent to the addressee are encrypted with the same public key of the addressee. An attacker who hacks the addressee's private key can therefore decrypt all encrypted data objects transmitted to the addressee.